Rheostat



unirse STATES Patented Sept. 25, y

i @Hanna-iranienne iiiooniin, or enaninsron, sourir CAROLINA Application ined september is', 1924. 'serai no. 738,033.

lThis invention relates 'toL improvements "in `rhei'is'tats, and consists of the constructions,

combinations and arrangements herein describedand claimed. Y

An object of the invention. is to provide a lrheos'tat which permits the effective' use of alternating current for Welding purposes.`

Another object of theinvention is to provide a rheostat of the grid type having a sup- .pleinent'ary or auxiliary grid bythe particu' lar use of which alternating current may be adapted to welding/purposes'. y ,l Other objects'ai'id advantages ap 'ear'in the vfollowing specification, reference eing had to the accompanying drawing', in which Figure 1 is front ,elevationrof the iniproyed rlieostat. n :Fgure 21's a side elevation. n

4F'gure 3 is a f'liagrain illustrating the cirrcuit involved. f y r y A Fi ure4 is a'l detail'pla'n View of one of the' grid anks. l y. F y v u AFigure `5 is a detailsectional View of apportion of therheostat illustrating'tjlie particular manner ofinountiiig'the grids;v n

- In carrying out the invention use :is made of an open frame composed of uprights or legs suitable cross pieces 2 and a plurality of end cross bars 3. Theseare located at each end of the frame (Fig. 2), and there 'are three pairs of ythe cross/bars 3'to. support asV Vmany' banks of grids. The cross bars, legs,y

etc. are suitably astenedtogether as'by means f of rivets'. `A suitable".insulatingpanel 4 is `fastened to the front of the frame, covering y approximately one-halfof the distance.

Asmentioned before, there are' three banks, of grids. These are designated 5, f6 and 7.

'llliebank7 is called a supplementary or auxo liliary gridbank because by means of it and its control, alternating current has been found.

usable for welding purposes. F distinct ini-A roveinent in the mounting of the grid banks bank is mounted alike, the'vdescription ofthe mounting of the upper kbank 7 will sulicefioi' :the three. v y f Rods 8 and 9 extend from one cross bar 3 to the other. The ends of the rods are threaded to receive a pair of nuts 1() and 11 (Fig. 5).

fis then :fitted upon each end of the mica sleeve 412. i f n 'upper bank 7.

yIlias been Worked out, and inasmuch` asv each; y I n ,which are connected with certain ones oi the Amica washer lcornes next to the collar 14,an`d then follows a plurality of copper washersl `and metallic grids 17 in alternation. Figure 5 shows two of the grids 17 separated rointh'e i'ieXt similar set by a mica washer 18 on o'ne rodaiid connected byy a lug,`

40 onthe other rod to the next set of grids which is made inthe saine manner as the first and in; turn is connected by a lug 40 to the set following. Thus the lugs/10 andI mica wash- 'ers'18 alternate, yconnecting the parallel sets of grids' in series.

y yin the ban-1st ande a 'Slightly diam-ent 'arrangement prevails. In'both instances the `,grids are connected three in parallel. These vparallel sets are lthen connected in series. It is to' be noted that the only dilerence is that with 'ther contacts'p23 and 24; of the knife switcli25, the pivotal niountings of which arev connected by means of a wire 26 with the central grid bank 6, and a wire 27 with the handle of a' welding tool (see Fig.

' n A Wire 28 leads: from the usual ground connectioi'i to the` pivot 29 of a. single, primary knife switch 30. The switchfSO has a plurality of contactsfl which are respectively joined by means of suitable electrical conductors 32 with certain ones of the gridsfin the y l The switch controls approximately one-half of the upper bank.

' Similarly, a single blade, secondary knife switch 33 controls the other halfof the upper grid bank. The pivotal point. 34 of this` switch is connected in shunt by means of wire 35 lwith the Wire 28 at the pivot 29. The switch 33 has a. plurality of contacts 36 upper grids by'inejans of conductors 37.

A wire 39 connects the upper bank 7 w-ith the lower bank 5. A wire 38 connects the last contact 36 with a predetermined set grids inthe lower bank 5. Obviously -the connection 39 may be inadeadjustable, for example Cil CJI

ment ot' the connectors 32 and 37 as much so as of the wire 39, and the outstanding lugs l0 permit of such adjustment. 'I he connectors may be clipped on where desired.

Upon closure ot the switch 25 current tlows from the transformer mentioned over the wire f2? to the welding electrode holder, passing through the ground connection to the wire Q8. Presume that the primary switch 30 has been moved down far enough to engage the lirst contact 3l. All of the grids in the upper bank 7 must be traversed by the current before it reaches the wir-e 39 and enters the lower bank 5. Thence it passes to the bank (3, with which it is connected at 41, emerging at the wire 26 and returning to the source of supply.

1t is obvious thatfturther closing ot the primary switch 30 will cut out more of the grids in the bank 7 so that the resistance is lowered and the welding heat is increased. Should even greater' heat be needed than the manipulation ot the primary switch 30 will aitord, recourse is had to the secondary switch 33. Upon successive engagement of the contacts 36 more and more ot the grids in the upper bank will be cut out until the lastl contact 36 is engaged, whereupon even one section ot the lower grid 5 is cut out.

The main purpose of the invention is to provide a rheostat ot the grid type by means of which alternating current may be used in conjunction with bare welding electrodes Jfor making a weld. @ther and known types ot A. C. rheostats are able to use only the various makes ol coated electrodes. This coat forms a slag which maintains the are. This slag causes the deposited metal to be tall ot small holes .so that it assumes a spongy appearance which makes it totally unsuited for use in pla-ces where steam and water tight connections must be made.

The improved rheostat eliminates the present disad'antages, chietlyjby virtue of Vthe tact that it permits the use o'l bare electrodes with alternating current. Obviously, it is also possible to use coated electrodes when desired,but it isto avoid such use that the particular rheostat has been designed. The auxiliary bank of' grids T and the switches 30 and 33 which control themyprovide the necessary line adjustment of heat required to burn a bare electrode successfully. This type of rheostat may be used on practically any volt-age up to 550 by simply introducing the correct number ot sets of grids in the circuit.

I claim:

l. A rhcostat comprising a succession of insulated grid sections in series connection with a series oit successive sections forming part thereof provided with separate cut-out connection to successively arranged switch 'contact members, and a single blade switch member mounted for movement progressively to engage and connect in series said suecessive contact members whereby movement ot the switch blade to engage said contacts is ei'ectivcl progressively to decrease the grid rcsistance interposed in the circuit.

2. ,A rheostat comprising asuccession ot insulated grid. sections in series connection with a series ot successive sections'forming part thereof provided with sepa 1ate cut-out eonnec ions to successively arranged switch contact members, a single'switch 'member connected in shunt ar-oundsaid series aforesaid; and mounted for movement progressively to engage saidcontact members, first, to interpose said entire series in the resistance circuit, and thereafter progressively to cutout successive sections l'rom said circuit.

3. A rheostat comprising a plurality oit banks of grids in series connection, one of said banks comprising va succession'of insulated grid sections in series connection, each section being provided with individual cutout connection to successively arranged switch contact members, and a single switch member mounted -for movement progressivelyto engage and connect in series said successive individual cut-out contact members whereby movement of said switch member to engagesaid contacts progressively decreases the grid resistance interposed in the circuit.

It. A rheostat comprising a plurality of banks of grids in series connection, one oi' said banks comprising a succession of insulated grid sections in series connection, each section being provided with individual cutout connection to successively arranged switch contact members, and a single switch meinber mounted for movement progressively to engage and connect in series said successive individual cut-out contact members whereby movement ot said switch member to engage said contacts progressively decreases the grid resistance interposed in the. circuit, ,one of said other banks of grids having a series of successively arranged insulated grid sections, each with a connector element projecting therefrom.y and a connection from the -end or linal switch contact of the first mentioned bank selectively engageable with intermediate projecting connector elements of the second mentioned bank t'urther and selectively to decrease interposed grid resistance upon the tinal closing of the aforesaid switch member.

` THADDnUs BAKER Moonen y 

